Bonding dissimilar metals



Patented Dec. 6, 1927.

UNITED STATES 1,651,403 PATENT OFFICE.

.HARRY C. MOUGEY, OF DAYTON, OHIO, ASSIGNOR T0 GENERAL MOTORS RESEARCH CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE.

BONDING DISSIMILAR METALS.

i Application led January 23, 1923. Serial No. 314,462.

This invention relates to the uniting of dissimilar metals, such as copper and ferrous metals (iron or steel) in such a manner that an effective thermal contact will be secured whereby the copper body` may operatey etliciently to conduct heat away from the ferrous body.

One object of the present invention is to unite relatively thin coppermembers such as heat dissipatinolins to relatively thick ferrous bodies suc as the walls of an iron or steel engine cylinder, by a process involving the use of a bonding material which melts at a low temperature4 relative to the melting points of iron or copper.

Other and further objects and advantages of the present invention will be apparent from the following description of embodiments thereof, reference being made to the accompanying drawings.

In the drawings:

Fig. 1 is a side View of an engine cylinder constructed in accordance with the present invention.

Fig. 2 is a sectional view taken on line `2--2 of Fig. 1, this view being on an enlarged scale.

Fig. 3 is a. plan of the cylinder in the process of construction.

Fig. 4 is. a longitudinal sectional view of parts shown in Fig. 3.

A cylinder 30 of ferrous metal is machined on the outside to insure a good mechanical contact with the bases 33 of the in material 31 formed preferably of a continuons strip of tin material in such a manner as to provide tin loops 32 connected by tin bases 33. The cylinder 30 is coated with a flux such as zinc chloride and is then dipped in a lead bath and the excess lead is wiped oil.

The copper tins 32 are coated with sodium silicate dried on or coated with sodium silicate mixed with graphite dried on, but under the bases 33, when the fins are to unite with the cylinder, no such coating is applied. A soldering flux such as zinc chloride solution or zinc chloride and vaseline n'iixed (Burnleys soldering flux) is applied to the surfaces of the bases of the lin material to be united with the cylinder wall.

The tin material 3l is wrapped about the cylinder wall and is held temporarily in place in any convenient manner as by means of binding wires 35. This assembly of cylinder and fins is then immersed in a lead bath for a few minutes and removed, allowed to drain for about one second and then plunged in water. l

Some of the lead of the bath lfills the spaces between the lead coating on the cylinder and the fin bases 33 to form a lead coating which intermingles with the lead coating and with the lin material to' provide an intermediate bonding layer 34 between the ferrous metal of the cylinder and`the copper of the fins. This bonding layer provides a true ,thermal contact between the cylinder wall and the fins and serves to conduct heat from the cylinder wall satisfactorily to the fins.

It is desirable that the ferrous cylinder shall be thoroughly coated with lead before the inning material is assembled. In case of cast iron, the surface to be lead coated is first copper plated. If the ferrous metal be steel or malleable iron copper plating the surface will insure a good lead coating, or the surface may be cleaned with sulpihurie acid and coated with zinc chloride The lead bath is covered with zinc chloride lux to keep it clean, and should be maintained at a temperature slightly above the melting point.

It has been found that copper can be united to steel, mallable and cast iron by this process, the ferrous body being coated with tin or lead-tin alloy instead of lead only. A coating bath of 50% lead and 50% tin solder has been used successfully.

Iron plating of the surface of cast iron to be coated -is more satisfactory than simply copper plating since the copper plating on the cast iron may dissolve away in the lead before the iron is coated.

A preferred method of attaching fin material to a cast iron cylinder is as followsz-The lin material is assembled within a tube 4() as shown in Fig. 3 and the spaces within the fin loops 32 and between the 1in loops and the tube are packed as indicated at 41 with a mixture of core sand and a suitable flux such as zinc chloride so as to leave only the bases 33 of the fins exposed. This mold is hardened by baking in an oven until free from moisture. The cast iron cylinder is iron plated and lead coated and then covered with a strong solution of flux such as zinc chloride. The exposed bases of the fins are wet with zinc chloride solution or other suitable linx solution, and the cylinder 30 is slid into the mould, which may be supported by a collar 42 held temporarily by a set screw 43. The assembly is heated in an oven to about the melting oint of lead and is then immersed in a bat of melted lead or lead with a small percentage of tin for two or three minutes. The assembly is removed ,and drained for a few seconds and quenched in Water.

This process produces an engine cylinder of ferrous metal having joined thereto a series of relatively thin copper fins by means of an intermediate bonding element having a relatively low melting point as compared with copper and iron. The lead coating on the ferrous metal is believed to intermingle with the ferrous particles or attach itself thereto in such a manner as to provide a good thermal contact between the iron and the lead coating. The lead coating unites relatively easily with the copper iin material when heated. Hence the copper is attached to the ferrous metal in such a manner that the bond offers relatively little resistance to the transfer of heat. Therefore the fins may operate effectively to dissi ate heat from the ferrous Walls of the cylin er. It is contem plated that the fins shall be exposed to a draft of cooling air which, so to speak, wipes the heat away from the fins.

After the assembly is removed from the soldering bath, it may be drained several seconds if it be rotated with its axis horizontal, after which the assembly is quenched in water.

It is important that the fin material be clamped sufficiently tight against the cylinder that the spaces between the fin material and cylinder will be small. Then the molten lead will be held in position by ca illarity and will not all run away before coo ing.

Copper fin material can be joined to a steel cylinder by the same process. The

steel cylinder is preferabl before coating with lead iron plated. s

The precoating of the ferrous cylinder with the bondin material shortens the time for making the nd between the thin copper fins and the cylinder hence materially reduces the amount of copper dissolved b the lead when the assembly of fins and cy inder is heated in the lead bath. If the ferrous body were not previously lead coated copper plated ut need not be before the assembly is dipped into the lead, then much more time would be required for making the bond because of the time required for the lead to soak the ferrous body, and much more of the fin material would be dissolved in the lead.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What I claim is as follows:

1. The process of joining to an iron body of a higher heat conducting metal, which consists in coating the surface of the iron body with a soft soldering material, applying suitable flux to those surfaces of the fins that are to be united to the iron body, assembling the fins'in proper position with the iron bod and dippin the assembled iron body an fins in a so der bath, while preventing by a suitable protective covering, the solder of the bath from adhering to the exposed surface of the fins.

2. The proce of a copper member to a ferrous metal member which consists in plating the ferrous metal member with a metal havin a higher melting int than that of the nding material to used to unite said members, dippi the plated ferrous metal member in a mo ten bath including lead, aembling the co per member and the coated ferrous mem r and holding them in engagement with one another, immersing the assembly thus formed in a bath of molten bonding material including lead, and in finally removing the assembly from the bath and cooling the same.

3. The proce of uniting a copper member or part to another member made of ferrons metal which consists in plating the ferrous metal with iron throughout the area of contact between said members, dipping the plated ferrous metal member in a molten bath including lead, assembling the copper and plated and coated ferrous metal members and holding them in engagement with one another, dipping the assembly thus formed in a hath of molten bonding material including lead, and finally removing the assembly from the bath and cooling the same.

In testimony whereof I hereto ax my signature.

HARRY C. MOU'GEY. 

